Atm multicasting for delivering information over a network

ABSTRACT

A method that provides for multicast delivery of information in a DSL network includes creating transmission paths between a single source port and multiple destination ports in a DSL network; receiving information at the source port; determining which of the destination ports is to receive the information; and distributing the information from the source port to selective ones of the destination ports based on the prior referencing step. A DSL system for providing multicast delivery of information includes an ATM network layer for sending information, a digital subscriber line access multiplexer (DSLAM) coupled to the ATM network layer for receiving the information, and a network control system for controlling selective multiplexing of the information through the digital subscriber line access multiplexer (DSLAM).

FIELD OF THE INVENTION

[0001] The present invention generally relates to network communicationsand, more particularly, to a method of ATM multicast distribution at anATM network layer.

BACKGROUND OF THE INVENTION

[0002] Changing communications demands are transforming the existingpublic information network from one limited to voice, text and lowresolution graphics to bringing multimedia, including full motion video,to everyone's home. A key communications transmission technology that isenabling transformation of existing public information networks toaccommodate higher bandwidth needs is Asymmetric Digital Subscriber Line(ADSL), a modem technology. ADSL converts existing twisted-pairtelephone lines into access paths for multimedia and high-speed datacommunications. ADSL can transmit up to 8 Mbps (Megabits per second) toa subscriber, and as much as 960 kbps (kilobits per second) or more inboth directions. Such rates expand existing access capacity by a factorof 50 or more without new cable installations.

[0003] Asymmetric Digital Subscriber Line ADSL technology involvesmodems attached across twisted pair copper wiring in which transmissionrates can be up to 8 Mbps downstream (to the subscriber) and from 16kbps to 960 kbps upstream (from the subscriber), depending on linedistance, can be achieved. Asynchronous Transfer Mode ATM is an ultrahigh-speed cell based data transmission protocol that may be run overADSL. A Digital Subscriber Line Access Multiplexer (DSLAM) is a devicethat takes a number of ADSL subscriber lines and concentrates them to asingle ATM line. Plain old telephone service POTS refers to basic analogtelephone service. POTS takes the lowest 4 kHz bandwidth on twisted pairwiring. Any server sharing a line with POTS must either use frequenciesabove POTS or convert POTS to digital and interleave with other datasignals.

[0004] Audio, video and other information is increasingly beingdistributed over networks from a single source to multiple destinationpoints on the network. Networks have finite bandwidth capacitiesassociated with them. Sending multiple copies of the same information tomultiple destinations can become demanding on the network and does notconstitute an efficient use of resources.

[0005] Accordingly, there is a need for implementing a multicastdelivery service in a DSL network to make efficient use of the network.

SUMMARY OF THE INVENTION

[0006] A method that provides for multicast delivery of information in aDSL network includes creating transmission paths between a single sourceport and multiple destination ports in a DSL network; receivinginformation at the source port; determining which of the destinationports is to receive the information; and distributing the informationfrom the source port to selective ones of the destination ports based onthe prior referencing step.

[0007] A DSL system for providing multicast delivery of informationincludes an ATM network layer for sending information; a digitalsubscriber line access multiplexer (DSLAM) coupled to the ATM networklayer for receiving the information; and a network control system forcontrolling selective multiplexing of the information through thedigital subscriber line access multiplexer (DSLAM).

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The advantages, nature, and various additional features of theinvention will appear more fully upon consideration of the illustrativeembodiments now to be described in detail in connection withaccompanying drawings wherein:

[0009]FIG. 1 is an exemplary digital subscriber line (DSL) systemarchitecture capable of offering integrated multi-line telephonyservices such as voice, data and video.

[0010]FIG. 2 is a block diagram of the inventive method of multicastdelivery of information in a DSLAM at the head-end of a DSL network.

[0011]FIG. 3 is an example of a multimedia setup request to network tojoin a point-to-multipoint ATM virtual circuit.

[0012] It should be understood that the drawings are for purposes ofillustrating the concepts of the invention and are not necessarily theonly possible configuration for illustrating the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention is a method of ATM multicasting at the ATMnetwork layer in a DSLAM at the head-end network for the purpose ofdistributing information, such as real-time data, video or audio, to thecustomer premise equipment CPE. The ATM layer multicast delivery serviceenables a source to transmit ATM cells from a single point to multipledestinations (point-to-multipoint), rather than using traditionalbroadcast or uni-cast distribution methods. This can be viewed as an ATMvirtual path/virtual circuit with a single source and multipledestinations. The ATM network layer will deliver the ATM cells (on amulticast basis) to the destination points specified in the ATM virtualpath/virtual circuit connection profile. By implementing a multicastdelivery service in a DSLAM at the head-end of a DSL network it ispossible to make efficient use of network resources for the purpose ofdistributing audio, video and other information to the customer premise.

[0014] A DSL system architecture 1 for integrating voice, data and videoservices, shown in FIG. 1, is presented as an exemplary DSL environmentfor employing the inventive method of enabling video phone communicationand similar multimedia communication over a DSL link. Details of theindividual block components making up the system architecture are knownto skilled artisans, and will only be described in details sufficientfor an understanding of the invention. The system block diagram 1 iscomposed of several functional blocks. The system domain is composed ofCentral Office (CO) Equipment 100 and Customer Premise Equipment (CPE).The component blocks within the system domain and their respectiveinterfaces are: customer premise equipment (CPE), Digital SubscriberLine Access Multiplexer (DSLAM) 9, an ATM switch 2, an IP router 13 andDSL terminator 12, and a network control system (NCS) 11.

[0015] The current customer premise equipment (CPE) 2 includes a DSLmodem unit that interfaces with four separate analog telephones 3-6 overa plain old telephone service (POTS), a 10Base-T Ethernet connection toa PC desktop system 7, and an Ethernet or RS-422 connection to a set-topbox with a decoder 8 for connection to a television or video display 8′.From the customer's analog end, the CPE device 2 accepts the analoginput from each of the telephones 3-6, converts the analog input todigital data, and packages the data into ATM packets (POTS over ATM),with each connection having a unique virtual channel identifier/virtualpath identifier (VPI/PCI). Known to skilled artisans, ATM is aconnection oriented protocol and as such there is a connectionidentifier in every cell header which explicitly associates a cell witha given virtual channel on a physical link. The connection identifierconsists of two sub-fields, the virtual channel identifier (VCI) and thevirtual path identifier (VPI). Together these identifiers are used atmultiplexing, de-multiplexing and switching a cell through the network.VCIs and VPIs are not addresses, but are explicitly assigned at eachsegment link between ATM nodes of a connection when a connection isestablished, and remain for the duration of the connection. When usingthe VCI/VPI, the ATM layer can asynchronously interleave (multiplex)cells from multiple connections.

[0016] The Ethernet data is also encapsulated into ATM cells with aunique VPI/VCI. The ATM cell stream is sent to the DSL modem to bemodulated and delivered to the DSLAM unit 9.

[0017] Going in the other direction, the DSL signal is received anddemodulated by the DSL modem in the customer premise equipment 2 anddelivered to VPI/VCI detection processing. The ATM cell data withVPI/VCI matching that of the end user's telephone is then extracted andconverted to analog POTS to be delivered to the telephone. The ATM celldata with VPI/VCI matching that of the end user's Ethernet is extractedand delivered to an Ethernet transceiver for delivery to the port.

[0018] The Digital Subscriber Line Access Multiplexer DSLAM 9demodulates data from multiple DSL modems and concentrates the data ontothe ATM backbone network for connection to the rest of the network. ThatDSLAM provides back-haul services for package, cell, and/or circuitbased applications through concentration of the DSL lines onto ATMoutputs to the ATM switch 10.

[0019] The ATM switch 10 is the backbone of the ATM network. The ATMswitch 10 performs various functions in the network, including celltransport, multiplexing and concentration, traffic control and ATM-layermanagement. Of particular interest in the system domain 100, the ATMswitch provides for the cell routing and buffering in connection to theDSLAM, network control system 11 and the Internet gateway (InternetProtocol IP router 13 and DSL terminator 12), and T1 circuit emulationsupport in connection with the multiple telephony links switch 15. A T1circuit provides 24 voice channels packed into a 193 bit frametransmitted at 8000 frames per second. The total bit rate is 1.544 Mbps.The unframed version, or payload, consists of 192 bit frames for a totalrate of 1.536 Mbps.

[0020] The ATM switch 10 is shown coupled to a program guideserver/video server 16 to satellite 17, radio broadcast 18 or cable 19networks. The ATM switch 10 is also coupled over the DSL terminator 12and IP router 13 pair to receive Internet Protocol IP packet data fromthe Internet 14.

[0021] The network control system 100 provides for address translation,demand assignment and call management functions. The Network ControlSystem's principle function is to manage the DSL/ATM network includingthe origination and termination of phone calls. The NCS is essentiallythe control entity communicating and translating control informationbetween the class 5 PSTN switch (using the GR-303 protocol) and the CPE.The network control system 100 is available for other functions such asdownloadable code to the CPE, and bandwidth and call management (e.g.,busy) functions, as well as other service provisioning and set up tasks.

[0022] Turning now to FIG. 2, the block diagram 20 illustrates ATMmulticasting at the ATM layer at the head-end of the network for thepurposes of distributing audio, video and other information to thecustomer premises equipment CPE. Multicasting is an efficient method ofdata delivery that simultaneously sends information to a group ofinterested destination points. Networks have finite bandwidthcapacities. Sending multiple copies of the same information to multipledestinations can become demanding on the network and does not constitutean efficient use of resources.

[0023] The DSLAM of FIG. 2 is configured with an ATM trunk port 21 andmultiple destination ports 22-28. The ATM trunk port 21 is a singlevirtual path/virtual channel, illustratively assigned a VPI of 39 and aVCI of 12. In this exemplary ATM multicast/point-to-multipointdistribution information is delivered from the ATM trunk port 21 tomultipoint destinations: ADSL port 1 22, ADSL port 2 23, ADSL port 4 25and ADSL port N 28. ADSL port 1 22 is assigned a VPI of 36 and VCI of21. ADSL port 2 23 is assigned a VPI of 36 and VCI of 20. ADSL port 4 25is assigned a VPI of 45 and VCI of 9. ADSL port N is assigned a VPI of37 and a VCI of 4.

[0024] ATM multicasting can be done at the ATM network layer. The ATMnetwork layer is responsible for cell header generation and extraction,cell VPI/VCI translation and cell multiplexing and de-multiplexing. Whena cell arrives at the trunk port it is identified as a channel of videoor other information. This is based upon the arrived cell's VPI/VCI pairindicated in the cell header, which is a relationship known by thenetwork control system. A connection profile can be referenced to findthe subscribers to this particular ATM virtual circuit. Based upon theconnection profile, ATM cells can be duplicated to the group ofcustomers subscribing to this channel.

[0025]FIG. 3 shows an example of a multimedia setup request to networkto join a point-to multipoint ATM virtual circuit.

[0026] The Customer Premise Equipment (CPE) sends a request to thenetwork for a multimedia program on an ATM signaling virtual circuit (1,FIG. 3). The message is sent to the ATM switch based on the ATMsignaling virtual circuit (2, FIG. 3). The message is sent to theNetwork Control System (NCS) based on the ATM signaling virtual circuit(3, FIG. 3). The Network Control System (NCS) determines if the requestis valid (4, FIG. 3). If it is a valid request, it sends a request tothe Multimedia server for the CPE to join/build amulticast/point-to-multipoint ATM virtual circuit for the selectedchannel (5, FIG. 3). The Network Control System (NCS) sends a request tothe ATM switch for the CPE to join a multicast/point-to-multipoint ATMvirtual circuit for the selected channel (6, FIG. 3). The NetworkControl System (NCS) sends a request to the Digital Subscriber LineAccess Multiplexer (DSLAM) for the CPE to join amulticast/point-to-multipoint ATM virtual circuit for the selectedchannel (7, FIG. 3). Once this connection has been made, the multimediainformation will flow to one or more CPE end-nodes (8, FIG. 3).

[0027] In order to provide support for the delivery of multimediaservices in a DSL network, an economies of scale needs to be achievedfor the service provider in order to cost effectively deliver theseservices to the end user. This economies of scale can be achieved byefficiently using network resources during the delivery of thismultimedia information to the end user. In order to efficiently delivermultimedia to the end user a concept known as multicast can be employedin the network. The basic principle of multicast is the delivery of asingle stream of information to many while efficiently using theresources of the network. It efficiently uses the resources of thenetwork by having the server only send a single copy of the multimediaprogram and having downstream intermediate nodes replicate this programuntil it reaches the necessary end users. Broadcasting is ineffective atproviding this, unless every end user is requesting the multimedia.

[0028] The ideal place for effective multicasting is at the edge of thenetwork. The edge device in a Digital Subscriber Line (DSL) network isthe Digital Subscriber Line Access Multiplexer (DSLAM). The DSLAM shallhave the capabilities of setting up point-to-multipoint connections atthe ATM layer (i.e., a multicast connection). By having this function,the DSLAM can replicate data and send it to multiple subscribers ondifferent ports.

[0029] The uniqueness of this invention is the method by which themulticast/point-to-multipoint ATM virtual circuits are set up for thedelivery of information to the end user. Also, that the system providesthe control for the multicast/point-to-multipoint delivery ofinformation to the end user.

[0030] Although the embodiment which incorporates the teachings of thepresent invention has been shown and described in detail herein, thoseskilled in the art can readily devise many other varied embodiments thatstill incorporate these teachings.

1. A method for multicast delivery of information in a DSL networkcomprsing the steps of: creating transmission paths between a singlesource port and multiple destination ports in a DSL network; receivinginformation at said source port; determining which of said destinationports is to receive said information; and distributing said informationfrom said source port to selective ones of said destination ports basedon said step of referencing.
 2. A method according to claim 1, whereinsaid step of creating comprises creating paths between said source portand said destination ports that can be selectively multiplexed in adigital subscriber line access multiplexer DSLAM.
 3. A method accordingto claim 1, wherein said step of distributing comprises multiplexingsaid source port to said selective destination ports in a digitalsubscriber line access multiplexer DSLAM.
 4. A method according to claim1, wherein said step of receiving comprises receiving said informationat an ATM trunk port of a digital subscriber line access multiplexer. 5.A method according to claim 1, wherein said step of determiningcomprises determining which destination ports are associated with userswho have subscribed to receive said information.
 6. A method accordingto claim 1, wherein said. Step of determining comprises referencing aconnection profile to determine destination ports for said information.7. A method according to claim 1, wherein said step of receivingcomprises receiving said information at an ATM trunk port of a digitalsubscriber line access multiplexer and said step of distributingcomprises multiplexing said source port to said selective destinationports in a digital subscriber line access multiplexer DSLAM.
 8. A methodaccording to claim 1, wherein said step of receiving comprises receivingsaid information at an ATM trunk port of a digital subscriber lineaccess multiplexer, said step of determining comprises determining whichdestination ports are associated with users who have subscribed toreceive said information, and said step of distributing comprisesmultiplexing said source port to said selective destination ports in adigital subscriber line access multiplexer DSLAM.
 9. A DSL system forproviding multicast delivery of information comprising: an ATM networklayer for sending information; a digital subscriber line accessmultiplexer (DSLAM) coupled to said ATM network layer for receiving saidinformation; and a network control system for controlling selectivemultiplexing of said information through said digital subscriber lineaccess multiplexer (DSLAM).
 10. A DSL system according to claim 9,wherein said ATM network layer is included in an ATM switch.
 11. A DSLsystem according to claim 9, wherein said digital subscriber line accessmultiplexer DSLAM comprises an ATM trunk port for receiving saidinformation from said network layer and destination ports for receivingsaid information selectively.
 12. A DSL system according to claim 9,wherein said destination ports comprise ADSL ports.
 13. A DSL systemaccording to claim 10, wherein said network control system comprises aconnection profile to determine which of said destination ports toreceive said information from said ATM trunk port.
 14. A DSL accesssystem according to claim 9, wherein said digital subscriber line accessmultiplexer DSLAM comprises an ATM trunk port for receiving saidinformation from said network layer and ADSL ports for receiving saidinformation from said ATM trunk port.
 15. A DSL system according toclaim 14, wherein each of said ATM trunk and ADSL ports is assigned aunique combination of virtual path and virtual channel identifiers.